Alright, car is a 88 760GLE with a AW71 and B280F motor.

When I got it, it had been sitting for 2 years or so and it had a leaking injector, and blew a lot of fuel, replaced injectors, which stopped that problem, however, when going from a standstill, when cold or at operating temp (worse when cold) you press the accelerator, the tacho drops down to below 500, then if you let go of the accelerator, it will pick up again to idle, otherwise if you keep the accelerator in, the engine stalls out, particularly when below operating temp.

If you then tap the accelerator again, the engine will drop then pick up above 1000rpm and start pulling hard and move off, it's hardly noticeable after going for a drive on the freeway.

When driving along, you can lift the throttle and the revs drop to idle while the car keeps moving.

At idle it still runs a bit rich, hunts a bit and the plugs are black even though the first set only did about 70km's and a fair bit of idling.

I've changed the following:
02 sensor
Spark plugs, leads, distributor cap, rotor.
Fuel injectors.
Fuel and Air filter.
FPR with one from my spare b280 from a 90'

I've cleaned:
AMM (the engine did idle better after doing that though)
IAC (I think it stopped hunting quite so badly after doing that too)

I have d/c both knock sensors individually and the right bank makes a massive difference, while d/c the left back which it's wires have been fiddled/repaired/covered with electrical tape, it runs rougher, but not as crippling but I didn't check that side as thoroughly.

I've also swapped the relays around, pulled out the crank angle sensor plug at the back and the car died, and the water temp sender as well, which made the car run like utter crap.

The only thing I can think of now is that the torque converters stator isn't locking causing the engine to load up, the stall speed is only 1500 as well.

A mechanic at work (I'm an apprentice diesel mech) said AMM or Fuel pump when he heard it do it when in neutral, fiddling with the amm screw thing changes how badly it does it, but doesn't stop it, I don't have access to a fuel pressure gauge.

I have looked through the FAQ's and can't really find too much that applies, any new ideas would be good!